1. Field of Invention
The invention relates to a recording medium cassette and an image forming apparatus with the recording medium cassette.
2. Description of Related Art
The exists, as an image forming apparatus that forms an image onto a recording medium, an ink-jet recording apparatus, for example. The ink-jet recording apparatus records a predetermined image onto a recording medium supplied thereinto by ejecting ink droplets from nozzles. Generally, cut sheets are used in the ink-jet recording apparatus as the recording mediums. Since the application of the ink-jet recording apparatus has been recently widened, there are a number of requests to perform recording onto not only cut sheets but also a long length of recording medium (a roll of paper).
There are two types of printers that record an image onto a sheet drawn from a roll of paper. One type of printer includes a roll of paper that is directly attached to a body of the printer. The second type of printer includes a cassette having a roll of paper that is attached to a body of the printer. In the former printer, it is burdensome to attach the roll of paper to the printer body because the roll of paper is directly and rotatably attached to the body while a leading edge of the roll of paper, which is supplied into a sheet supply port for conveying the sheet to a printing position, is prevented from coming out therefrom when attaching the roll of paper to the body.
Japanese Laid-Open Utility Model Publication No. 5-86541 (pages 6–9 and figures 1–3) discloses a structure for accommodating a roll of paper in a printer of the latter type, wherein a detachable rolled sheet holder (cassette) is attached to an equipment (printer) body. The printer body includes a printing portion having a pair of receiving rollers and a holder mounting portion to which the rolled sheet holder is attached. In order to place a roll of paper into the rolled sheet holder, first, the roll of paper is attached to the rolled sheet holder so as to be rotatably supported. A leading edge of the rolled sheet is then pinched between a first roller shaft and a second roller shaft which is urged toward the first roller shaft by a spring. Then, when the rolled sheet holder, having the roll of paper, is slidingly attached to the holder mounting portion of the printer body, a guide roller, provided at an end of the first roller shaft, rotates the sheet by a roller guide portion provided in the printer body. Thus, the leading edge of the rolled sheet, pinched between the first and second roller shafts, reaches the pair of receiving rollers provided in the printing portion. As described above, the leading edge of the rolled sheet can be easily taken into the printing portion of the printer body so that an operation of attaching the roll of paper becomes easy.
In the common ink-jet recording apparatus using a roll of paper, a leading edge of the rolled sheet is positioned at a start of a sheet conveying path while the roll of paper is disposed at an upstream position in a sheet conveying direction. Then, the sheet drawn from the roll of paper is conveyed to a printing position to perform a printing operation. However, because a sheet with a long length is wound into a roll, the sheet is curled. Especially, because a leading edge portion of the sheet is free from restraint, the leading edge portion tends to curve when the sheet is conveyed. Thus, when an image is recorded onto the sheet drawn from the roll of paper, ink droplet landing accuracy degrades due to the curl of the sheet, thereby deteriorating an image printing quality.
Japanese Laid-Open Patent Publication No. 10-279151 (pages 2–3 and figures 2, 3) discloses an ink-jet recording apparatus that resolves the above problems. In this ink-jet recording apparatus, first, a leading edge of a sheet drawn from a roll of paper loaded in a rolled sheet holder is pinched between auxiliary sheet supply rollers. Then, the sheet is pinched between a pair of correcting rollers. When the auxiliary sheet supply rollers rotate in this state, a curl caused on the rolled sheet is corrected by passing between the correcting rollers. Accordingly, the deterioration of the printing quality due to the curl of the rolled sheet can be restricted.
Furthermore, in the rolled sheet accommodating structure of the printer disclosed in Japanese Laid-Open Utility Model Publication No. 5-86541, the rolled sheet holder may rattle with respect to the printer body when the sheet is drawn from the roll of paper that is supplied to the printer body from the rolled sheet holder. The rolled sheet holder may rattle because the rolled sheet holder is merely attached to the printer body. Due to the rattling of the rolled sheet holder, the continuous sheet may not be conveyed in a direction parallel to the sheet conveying direction, thereby causing a sheet conveying failure.
In the ink-jet recording apparatus disclosed in Japanese Laid-Open Patent Publication No. 10-279151, a user needs to manually pinch the leading edge portion of the sheet drawn from the roll of paper, between the auxiliary sheet supply rollers. As such, the leading edge portion may not be positioned at the same position at all times. For example, the leading edge portion of the sheet is located at a position short of the auxiliary sheet supply rollers (at a position upstream of the auxiliary sheet supply rollers in a sheet conveying direction). When this happens, the sheet cannot be conveyed to the printing position.
There are two types of ways to set a roll of paper in an ink-jet recording apparatus. One way is that a roll of paper is loaded into a rolled sheet holder integrally provided to a printer body like the printer disclosed in Japanese Laid-Open Patent Publication No. 10-279151. Another way is that a roll of paper is attached to a printer body via a detachably cassette with respect to the printer body. In the latter way, the cassette can be removed from the printer body, so that there is flexibility in setting of the roll of paper. However, in both occurrences, the above-described problems may occur.